Concerning the surfaces of cells of Staphylococcus pyogenes. I. A pseudocapsulation phenomenon under certain experimental conditions.

A strain of pathogenic Staphylococcus aureus, grown under special conditions, accumulates extracellular metabolites about the bacterial cells. This phenomenon may simulate, but is differentiable from, the capsulation of, for instance, the mucoid "Smith" strain. The special nutrient requirements, namely lactose, mannitol, vitamin, and gelatin containing medium, promote the production and accumulation about the cells of, in particular, soluble coagulase. A mutant of this parent strain, deficient in capacity to elaborate soluble coagulase and fibrinolysin, does not accumulate metabolites about its cells, even under the special growth conditions. To avoid confusing this phenomenon, which at least in vitro is essentially artifactitious, with true capsulation, we suggest the term pseudocapsulation.